Concatenate and Test if Empty

Concatenate and Test if Empty does exactly two things, and it does them in one node: it glues together up to four text inputs into a single string, and it tells you whether that string ended up empty. That second half is the part worth having. "Is this prompt actually blank?" is a question you can't ask easily in a stock ComfyUI graph, and it's the key to building workflows that decide their own behavior.

The obvious use is conditional prompt assembly. Build a prompt out of pieces - a style tag from one node, a subject from another, a LoRA trigger word from a third - then branch on whether the result is empty: if there's nothing to say, route around the text encoder and save the run; if there is, encode it and sample. It's the text equivalent of a sanity check before you let a workflow spend minutes on an empty prompt.

How it works

The node takes up to four optional strings, appends each non-null one in order, then compares the result against an empty string:

result = ""
for t in (text1, text2, text3, text4):
    if t is not None:
        result += t
is_empty = result == ""

Everything worth knowing is in that loop. Nothing gets skipped except None - empty strings still count as content (though they contribute nothing to result). And note there's no separator inserted: "cat" + "dog" becomes "catdog", not "cat dog". If you want spaces or commas between parts, you have to put them in the inputs yourself.

Inputs and outputs

• text1–text4 (STRING, all optional) - the pieces to join. In practice these arrive as wires from upstream text nodes, so you can leave any of them disconnected.
• is_empty (BOOLEAN) - the first output socket. True when the combined result is blank.
• result (STRING) - the second output socket, the joined text itself.

The output order trips people up: is_empty comes first, result second. It's easy to assume the string is on top and wire the boolean into a text sink (or vice versa). Look at the socket names, not positions.

Installing it

Part of the Skycoder Tools pack:

cd ComfyUI/custom_nodes
git clone https://github.com/skycoder182/comfyui-skycoder-tools.git
# then restart ComfyUI

Or ComfyUI Manager → "Install Custom Nodes" → search "Skycoder Tools" → Install → restart. No models, no special dependencies.

Common issues

The separator thing is the classic trap - if your joined prompt reads like one long word, that's by design, not a bug. The other one is treating "empty" as "whitespace only": a string of spaces isn't empty by this node's definition (" " == "" is false), so a prompt of pure whitespace will sail through as non-empty. If that matters, trim upstream. And remember it's optional-input based, so with nothing wired it returns ("", True) - an empty result and a true is_empty, which is the correct boring answer.